1. Technical Field
The present invention relates to an electro-optic device substrate, an electro-optic device, an electronic apparatus, and a method for manufacturing the electro-optic device substrate.
2. Related Art
In general, electro-optic devices, such as liquid crystal display devices, use an electro-optic device substrate including TFT (thin film transistor) elements as switching elements and peripheral circuits. In such electro-optic devices, pixels are formed increasingly more precisely and finer to increase the amount of displayed information and enhance the display quality. Accordingly, the TFT elements, and eventually the contact areas of the TFT elements with wires, tend to be reduced more and more. Consequently, the contact resistance between the TFT element and the wire is increased, thereby causing writing failures, such as lack of written data.
In order to prevent the increase in contact resistance, for example, Japanese Unexamined Patent Application Publication No. 2005-203675 has disclosed that a layer is formed between the source/drain region and the wire, and that the connection between the TFT element and the wire is established in this layer.
In addition, the increase of the contact resistance between the TFT element and the wire can occur due to the following reason. For example, when a contact hole is formed in an insulating interlayer overlying the source/drain region of the TFT element, the contact hole undesirably passes through the silicon layer of the source/drain region, so that the contact between the wire and the silicon layer may be established at the section of the silicon layer. This is caused when the etching rate for forming the contact hole is varied. In this instance, the contact area between the wire and the source/drain region is reduced to increase the contact resistance.
In order to prevent the increase in contact resistance caused by the above reason, Japanese Unexamined Patent Application Publication No. 2005-158935 has disclosed a technique in which an electroconductive relay layer is formed over the source/drain region to prevent the contact hole from passing through the silicon layer.
Unfortunately, those techniques for preventing the increase in contact resistance require an additional photomask, and thus make the manufacturing process complicated.